Run some unit tests on all platforms

InternalTests can be run on all platforms since they have nothing
Linux-specific.

run_tests.py

@@ -20,9 +20,11 @@ from mesonbuild import mesonlib
 
 if __name__ == '__main__':
     returncode = 0
+    print('Running unittests.\n')
     if mesonlib.is_linux():
-        print('Running unittests.\n')
         returncode += subprocess.call([sys.executable, 'run_unittests.py', '-v'])
+    else:
+        returncode += subprocess.call([sys.executable, 'run_unittests.py', '-v', 'InternalTests'])
     # Ubuntu packages do not have a binary without -6 suffix.
     if shutil.which('arm-linux-gnueabihf-gcc-6') and not platform.machine().startswith('arm'):
         print('Running cross compilation tests.\n')